Evan Curtin


To determine the melting point of benzylamine to clarify inconsistent data


A sample of benzylamine is sealed in a screw-cap half-dram vial with parafilm then cooled in an acetone bath with dry ice.


Picture 1 showing the sample still liquid at -78 C [Excellent photo! AL]




The sample did not solidify even at -78 C. This is likely due to the impurity of the sample from the H NMR, estimated at only about 84% based on the integration of peaks at 3.8 and 4.8 ppm. Judging from the peaks at 4.84, 7.81 and 8.39 the impurity has an aromatic ring with a benzylic carbon. The impurity is more than likely a derivative of benzylamine, but the exact identity is not clear. [What is the impurity? How did it get there? AL]


The measurement of the freezing point of benzylamine must be redone with a sample of much higher purity.


10:57 - Added benzylamine to 1/2 dram screw cap vial, sealed with parafilm. Made a bath of acetone in a 250mL beaker. Added some dry ice to the bath.
11:02 - Bath temperature is -13C, added sample.
11:22 - Sample is still liquid, added more dry ice to cool further. Cooled to -30C [What is the limit to how low your thermometer can measure? AL][The thermometer can measure to -100C - EC]
11:32 - Added excess dry ice to the acetone. Solid pieces of dry ice were in the liquid. The sample did not freeze, but became viscous.
11:40 - Took pic1 showing the sample still liquid at -78C
11:40 - Prepared solution of benzylamine and CDCl3
11:45 - Took HNMR-1 of benzylamine using 500MHz varian NMR.